In many consumer packaging applications, it is important to prevent air or water or the like from passing out of or into a package containing certain products. This is particularly true with respect to meat packages, cheese packages, and the like, for which the contained product must be kept in a constant environment to prevent spoilage. It is also important to protect such products from tampering. In order to preserve the integrity and safety of a product contained within such a package, the periphery of the package must be hermetically sealed. Hermetic seals can be provided by both permanent seals and temporary seals known as peelable seals. Peelable seals are capable of providing a hermetic seal and, at the same time, providing a consumer with access to the contents of a package. A consumer breaks a peelable seal of a package by first grabbing onto opposing film faces to which peelable seal materials are adhered and then pulling the film faces apart. To provide a peelable seal on a package with a reclosable zipper, the package typically uses permanent seals at its side edges and bottom edge and a peelable seal above or below the reclosable zipper at the mouth end of the package. In addition, the peelable seal may be arranged on either the flange/base portions of the zipper or on the packaging film adjacent to the flange portions.
There are a couple of typical approaches for forming peelable seals on reclosable packages having a top and bottom film. One typical approach adheres a multilayered film to each of the opposing inner surfaces of the packaging film (or zipper flange portions) along the length of the mouth end of the package. This results in a first multilayered film on the inner surface of the top film and a second multilayered film on the inner surface of the bottom film. A peelable seal is formed by heat sealing the first and second multilayered films to one another. When a consumer breaks the peelable seal, one or more layers of the second multilayered film will disengage from the other layers of the second multilayered film and remain adhered to the first multilayered film. As a result, the first multilayered film will include at least one additional layer when the peelable seal is broken. The above layer disengagement upon breaking the peelable seal is accomplished by using film layers composed of different polymeric materials and by exploiting the varying bond strengths between the layers.
Another typical approach adheres a layer of film to each of the opposing inner surfaces of the packaging film (or zipper flange portions) and introduces contaminants to one or both of the film layers. When the peelable seal is formed by heat sealing the layers to one another, the bond between them is weak due to the surface contamination. Breaking the peelable seal detaches the layers from one another.
The foregoing described general constructions of polymeric bags and specifically peelable seals create hermetically sealed reclosable packages. These constructions, however, have not adequately addressed the task of alerting consumers when such a peelable seal has been broken. Clearly, there is a need for a peelable seal design which provides tamper evidence indicative of a broken peelable seal.